State of LiFePO4 Li-Ion Battery Electrodes after 6533 Deep-Discharge Cycles Characterized by Combined Micro-XRF and Micro-XRD

Recycling of Li-ion batteries is going to be a major challenge in the coming years in order to preserve the precious resources in battery materials. Within this challenge lies the task of identifying the state of the materials in the used batteries in order to determine the recyclability of the material. In this paper, we investigate the state of a set of LiFePO4 electrodes from A123 18650 graphite-LiFePO4 cells, which have been cycled continuously for 6.5 years (6533 cycles at a current rate of C/5). The spatially resolved morphological, chemical, and structural states of cycled as well as uncycled electrodes are mapped by sub-micrometer resolution synchrotron X-ray fluorescence spectroscopy and X-ray diffraction collected simultaneously over the same selected statistical relevant electrode areas (>100 000 μm2). The study reveals a very high morphological and chemical stability of the LiFePO4 electrodes and underlines the structural robustness of the olivine LiFePO4 structure. These findings highlight the potential for low-process recycling of LiFePO4 electrode materials.